Isolation and structure elucidation of new myrsinane-type diterpene polyesters from Euphorbia falcata L.

Diterpenes occurring in plants of the Euphorbiaceae family are of considerable interest as concerns natural product drug discovery programs because of the wide range of potentially valuable biological activities and the broad structural diversity due to the different polycyclic and macrocyclic skeletons and various aliphatic and aromatic ester groups.

In continuation of our investigations on diterpene content of Euphorbia falcata, ten compounds were isolated from the chloroform-soluble fraction of the MeOH extract of the plant. The present paper reports the isolation and structure determination of these diterpenes. The selected fractions were purified by RPC and preparative TLC to yield pure compounds. The structure elucidation was performed by extensive spectroscopic analysis, including 1D and 2D NMR (¹H-¹H COSY, HSQC, and HMBC), and HRESIMS experiments. The isolated compounds contain myrsinane, premyrsinane and cyclomyrsinane skeletons, esterified with acetic, propanoic, 2-methylbutanoic, isobutanoic, benzoic and nicotinic acids. Nine of them are new natural products and one is known (euphorprolitherin D) compound, isolated previously from the Asian species, E. prolifera. The compounds reported here are biogenetically related to those previously described from this species by our group. On the basis of the literature data, only E. falcata, and E. seguieriana has the unique diterpene profile, containing myrsinane, premyrsinane and cyclomyrsinane-type compounds together.

Acknowledgements: This work was supported by the European Union and co-funded by the European Social Fund TÁMOP-4.2.2.A-11/1/KONV-2012 – 0035.